1. Technical Field
This invention pertains to methods and apparatus utilized in surgical procedures involving fixation of soft tissue to bone tissue and, more particularly, to a novel method and apparatus for anchoring sutures to bone tissue to permit the aforesaid fixation.
2. Discussion of the Prior Art
As part of various endoscopic or arthroscopic surgical procedures, it is necessary to permanently attach a suture to bone tissue. For example, in certain procedures requiring suturing of soft tissue (e.g., muscle, cartilage, tendons, ligaments, etc.) to bone tissue, the suture must be anchored to the bone tissue before suturing can proceed. The prior art includes numerous suture anchors adapted to be secured in pre-drilled holes or tunnels in the bone tissue, and most of these anchors have one or more disadvantageous characteristics. Some prior art suture anchors are required to be hammered into the bone tunnel. These anchors are exemplified by U.S. Pat. Nos. 5,102,421 (Anspach, Jr.); 5,141,520 (Goble et al); and 5,100,417 (Cerier et al). Hammering (or impacting as it is often described) has the disadvantage of potential trauma and damage to surrounding bone tissue, and has limited applicability where the location of the bone tunnel is not axially aligned with an arthroscopic portal to permit transmission of the impacting force through an impactor to the anchor.
Some suture anchors are threadedly mounted in the bone tunnel, as exemplified by U.S. Pat. Nos. 5,156,616 (Meadows et al) and 4,632,100 (Somers et al). The screw insertion procedure tends to be time-consuming in that a pilot hole must first be drilled into the bone and then the hole may have to be tapped to receive the screw.
Many suture anchors involve an insertion procedure wherein the inserter device must partially enter the bone tunnel, thereby requiring a larger diameter tunnel than would be necessary for the anchor alone. Examples of such suture anchors are found in U.S. Pat. Nos. 5,037,422 (Hayhurst et al); 4,741,330 (Hayhurst); 4,968,315 (Gatturna) and 4,899,743 (Nicholson et al).
Most of the foregoing exemplar prior art suture anchors suffer from the disadvantage of being automatically deployed upon initial insertion into the bone tunnel. Specifically, such anchors typically have permanently projecting barbs, or the like, that are forced into the tunnel during initial insertion and preclude proximally directed movement in the tunnel after at least one barb engages the surrounding bone tissue. It sometimes happens that a particular tunnel turns out to be unsuitable, either because of location or configuration, but the surgeon does not recognize this until after the anchor has been inserted. With most prior art anchors there is no possibility of removing the inserted anchor; thus, a new tunnel must be drilled and a second anchor inserted. Accordingly, two (or possibly more) anchors may be left at the surgical site, only one of which is functional. This problem is addressed in U.S. Pat. No. 5,176,682 (Chow) wherein a suture anchor is disclosed as having normally retracted fins capable of being selectively projected radially to engage the bone tunnel walls in a barb-like manner. Selective projection of the fins is effected by hammering a pin axially through the anchor to force the fins radially outward. Prior to hammering the pin, the inserted anchor is readily removable from the bone tunnel, thereby permitting the surgeon to test the adequacy of the drilled tunnel and its location. If the tunnel is unsatisfactory, the anchor can be removed, rather than being left in place. Although this technique solves the problem of having an unused anchor left in an unsatisfactory tunnel, it has some other disadvantages. Specifically, permanent installation of the anchor requires tools (i.e., a hammer and impactor) that are separate and apart from the inserter. Additionally, during impacting, the pin may be inadvertently driven entirely through the anchor and thereby damage bone tissue at the closed end of the tunnel.